1. Field of Invention
The present invention relates, in general, to a method of monitoring an exhaust gas recirculation (EGR) system, and more particularly, to a method of monitoring an EGR system which monitors the efficiency of an EGR cooler and whether or not an EGR ratio is abnormal by separating and extracting a corrected value of ignition timing detected in response to the operation of the EGR system from a value of ignition timing detected at knocking, whereby a temperature sensor for monitoring the efficiency of the EGR cooler and monitoring whether or not the EGR ratio is abnormal is removed.
2. Description of Related Art
In general, the object of applying an exhaust gas recirculation (EGR) cooler in an EGR system is to lower the temperature of EGR gas through the EGR cooler so that the cooled EGR gas enters a combustion chamber to thereby lower the temperature of the combustion chamber. This reduces the area where knocking may occur and thus advances ignition timing to increase torque, thereby improving fuel efficiency.
In EGR systems, a very important control factor in several aspects is to control the temperature of EGR gas. Recent EGR systems are configured such that the temperature of the EGR gas is lowered using the EGR cooler.
When the amount of exhaust gas that is discharged is changed due to clogging of the EGR cooler, it is required to monitor the clogging of the EGR cooler since it is regulated by the on-board diagnostics (OBD). The clogging of the EGR cooler is monitored using a mass airflow (MAF) sensor disposed at the front end of a manifold absolute pressure (MAP) sensor.
The efficiency of the EGR cooler is a factor defined in the OBD regulations. In order to satisfy error code monitoring regulations on exhaust gas by the CARB of North America and EOBD monitoring regulations enforced in Europe, temperature sensors are disposed at the front and rear ends of the EGR cooler. The temperature sensors measure and compare the temperatures of EGR gas before and after passing through the EGR cooler, thereby monitoring the efficiency of the EGR cooler.
However, when the two temperature sensors are additionally disposed at the front and rear ends of the related-art EGR system together with the MAF sensor in order to monitor the clogging of the EGR cooler and the efficiency of the EGR cooler as such, the cost of components required for disposing the temperature sensors and the number of process steps required for mounting the temperature sensors are increased, thereby increasing the entire cost, which is problematic.
In addition, Korean Laid-Open Patent Publication No. 10-2006-0069627 also disclosed “METHOD OF CONTROLLING EGR COOLER.”
However, this method also requires a temperature sensor to be disposed in the EGR system. Accordingly, the problems of the increased cost of parts and the increased number of process steps cannot be overcome.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.